Electronic structure calculations are to be employed to identify the individual roles of active site residues in alpha-chymotrypsin, carbonic anhydrase, and pepsin. Aid in understanding the catalytic mechanisms is obtained from computed charge distributions, geometries, electrostatic potentials, and interaction energies. The x-ray crystal structures which have been determined for heme proteins, iron-sulfur proteins, flavo-proteins and other oxidation-reduction proteins show hydrogen bonds between the active centers and the apoprotein. Use of electronic structure calculations can extend this geometrical information to charge distributions and binding energies and thereby help to characterize the observed coupling between protein oxidation state and hydrogen bond conformation. They also yield insight into how these hydrogen bonds influence the redox potential of the proteins. Ab initio (all electron, exact Hamiltonian) methods are to be used in the calculations for the enzyme active sites and for the hydrogen bond model in redox proteins. This well-established approach is known to give quantitatively useful results for small organic and inorganic molecules and it is possible to utilize it for protein studies because of a recent advance in the computational efficiency of carrying out energy optimization. Amino-acid residues outside the active site and solvent molecules can be represented accurately by a procedure employing electrostatic potentials.